Getting serious about cellulosic ethanol

At the Detroit Auto Show on Sunday, GM officials announced that the company has bought a stake in Coskata, Inc., a startup ethanol company that plans to turn just about anything containing carbon -- cornstalks, tires, garbage -- into as much as 100 million gallons of ethanol by 2011.

The process is very different from distilling ethanol from corn. It will use heat to gasify crop residue, wood chips, and other feedstocks into hydrogen, carbon monoxide and carbon dioxide. Then its proprietary microbes will feed on those gases, creating ethanol as a waste product.

"This firm seems to have great leadership. They're ready," said Mary Beth Stanek, GM's director of environment and energy policy and commercialization.

GM, which has already promoted installation of E-85 pumps at gasoline retailers, will help Coskata with marketing of ethanol.

GM's investment in a new generation of ethanol production doesn't mean it's abandoning ethanol made from corn.

"We need both the corn ethanol and generation two ethanol. It's not one or the other. We need it all," she said.

It's going to be a while before Coskata's new process is more than a drop in the bucket of ethanol production that could hit 13 billion gallons by the end of 2008. The Warrenville, Illinois company plans a pilot plant that will make 40,000 gallons by the end of this year.

Others already involved in cellosic ethanol research questions Coskata's ability to ramp up from 40,000 gallons to 100 million by 2011.

Bill Roe, Coskata's CEO, told Agriculture Online that the technology used in the plant can be scaled up quickly.

"It's a very fair question. The whole concept of minimum-scale engineering is at play here," he said.

The microbes do their work inside ten-foot long tubes filled with membranes. That membrane technology is already used in water purification, Roe said. Inside the pipes are filaments as thick as electrical wire. Hydrogen gas and carbon monoxide move through the inside of the filaments. Anaerobic microbes feed on the gases, and release ethanol into water. The ethanol is separated from water using membranes as well.

Creating the gases used by the microbes is done with a plasma gasification process developed by Westinghouse. That generates temperatures hotter than the sun's surface -- 5,500 degrees Celsius. But the work of the microbes does not require high heat or pressure, said Wes Bolsen, the company's chief marketing officer.

The process uses less than one gallon of water to produce a gallon of ethanol, compared to three to four gallons of water needed ethanol made by conventional distillation methods, Bolsen told Agriculture Online. Using enzymes to break down cellulose instead of gasification requires six to seven gallons of water for a gallon of ethanol, he said.